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2-22
G R O U P 2-BRAKES
slowly by hand several times to let
air escape at the brake line fitting.
Hold the pedal d o w n and tighten the
brake line fitting. Release the brake
pedal. D o not release the brake pedal
until the fitting is tightened as addi-
tional air will be introduced into the
master cylinder.
O n trucks equipped with dash-
mounted booster, the cylinder can
be bled at the bleed screw on the
cylinder.
5. After seeing that the master
cylinder reservoir is filled with heavy-
duty brake fluid to within % inch of
the top of the filler neck, install the
outside of the cylinder and brake
line.
6. If the stoplight
switch is
mounted
on the master cylinder,
connect the stoplight switch wires to
the switch.
7. O n a truck with conventional
brakes, connect the rubber boot to
the end of the cylinder.
8. Check, and i f necessary, adjust
the brake pedal free-travel.
MASTER CYLINDER—P-SERIES
TRUCKS
REMOVAL
1. If the truck i s equipped with
a vacuum booster, the engine must
be stopped and all vacuum must be
expelled from the booster system
before the hydraulic lines are dis-
connected.
2. Turn the front wheels all the
w a y to the left, and remove the
fender apron attaching screws so
that the apron can be m o v e d to pro-
vide access to the master cylinder.
3. Disconnect the stoplight switch
wires from the switch.
4. Disconnect the brake line from
the brake tube fitting.
5. Force as m u c h brake fluid as
possible from the master cylinder
into a suitable container by pushing
d o w n the brake pedal all the w a y
several times.
6. Disconnect
the rubber
boot
from the end of the master cylinder.
7. R e m o v e the brake pedal return
spring, remove the cotter pin from
the clevis pin, and remove the master
cylinder push rod and boot. R e m o v e
the three mounting bolts and remove
the master cylinder from the mount-
ing bracket and away from the truck.
INSTALLATION
1. Assemble the master cylinder
to the mounting bracket and secure
with the three mounting bolts. Install
the push rod and boot to the front
of the master cylinder. Connect the
front end of the push rod to the
upper holes of the brake pedal ex-
tension with the clevis pin, and se-
cure with a cotter pin. O n a truck
equipped with a vacuum booster,
connect the push rod and insert the
clevis pin at the lower holes of the
pedal extension. Install the brake
pedal retracting spring.
2. Connect the brake line to the
master cylinder fitting, but leave the
brake line fitting loose.
3. Fill the master cylinder with
heavy-duty brake fluid to the speci-
fied level.
4. Push the brake pedal d o w n
slowly by hand several times to let
air escape at the brake line fitting.
Hold the pedal d o w n and tighten the
brake line fitting. D o not release the
brake pedal until the fitting is tight-
ened, as additional air will be intro-
duced into the master cylinder. Re-
peat this procedure until air ceases
to escape at the fitting and a firm
pedal is obtained.
5. After seeing that the master
cylinder reservoir is filled with heavy-
duty brake fluid to the specified
level, install the filler cap. Wipe off
the fluid from the outside of the cyl-
inder and brake line.
6. Connect the stoplight switch
wires to the switch.
7. Connect the rubber boot to the
end of the cylinder. Reposition the
fender apron and secure with the five
retaining bolts.
8. Check and, i f necessary, adjust
the brake pedal free travel.
VACUUM BOOSTERS—FRAME-
MOUNTED PISTON TYPE
REMOVAL
1. Depress the brake pedal sev-
eral times to remove all vacuum
from the system.
2. Loosen the booster air inlet
tube clamp, and remove the tube.
Disconnect the hydraulic lines and
the vacuum hose at the booster.
3. R e m o v e the booster mounting
bolts, then remove the booster. D o
not remove the breather or the vac-
u u m check valve unless operating
conditions indicate repairs are nec-
essary.
INSTALLATION
I, Position the booster on the
mounting bracket, and install the
mounting
bolts, using n e w lock-
washers.
2. Connect the hydraulic lines to
the booster. Tighten connections se-
curely.
3. Connect the air intake hose to
the control valve air inlet tube.
Tighten the hose clamp securely. If
necessary, clean the air inlet element.
4. Bleed the brake system as out-
lined
under
"Hydraulic
System
Bleeding," Part 2-1.
5. Connect the vacuum tube to
booster hose to the booster. Tighten
the hose clamps securely.
6. Perform the checks and tests
as outlined in Part 2-1.
VACUUM BOOSTERS—DASH-
MOUNTED-DIAPHRAGM TYPE
REMOVAL
1. Support the master cylinder
with a prop from the underside.
2. R e m o v e the master cylinder-to-
booster retaining nuts.
3. R e m o v e the clip that retains
the master cylinder outlet line to the
bracket on the dash panel.
4. Loosen the clamp that secures
the manifold vacuum hose to the
booster and remove the hose. Re-
m o v e the reservoir hose from the
booster unit, i f so equipped.
5. Pull the master cylinder off the
booster, and leave i t supported by
the prop far enough away to allow
removal of the booster assembly.
6. F r o m inside the cab, remove
the eccentric bolt and lock nut that
secure the booster valve operating
rod to the brake pedal. R e m o v e the
nuts that retain the booster mounting
bracket to the dash panel.
7. R e m o v e the booster assembly
from the engine compartment.
INSTALLATION
1. M o u n t the booster and bracket
assembly to the engine side of the
dash panel, by sliding the bracket
mounting studs and the valve oper-
ating rod in through the holes in the
dash panel.
2. F r o m inside the cab, install the
booster mounting bracket - to - dash
panel retaining nuts.
3. Position the master cylinder to
the booster assembly, install the re-
taining nuts, and remove the prop.
4. Position the master cylinder
outlet line to the bracket on the dash
panel, and install the retaining clip.
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